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ZANETTO, S. - The complex of St. Andrew and St. Peter the Elder's in Zadar (Croatia): the archaeology of standing building for the history of the early medieval city
This paper aims to reconstruct the diachronic development of the complex of St. Andrew and St. Peter the Elder's in the city of Zadar, from the 5th to the 12th century AD. The stratigraphic analysis of elevations allowed to learn the origin of the complex as well as its architectural and functional changes over time, from house or storage to place of worship. Therefore, this study provides new elements for understanding the 'second life' of the Roman city in Late Antiquity and Early Middle Ages. Furthermore, the analysis of the constructive techniques of the St. Peter the Elder's Church, particularly of the planimetric typology with rectangular inscribed apses and the system of cross vaults, contributes to knowledge of the workforces with their technological background, highlighting the role of Zadar as a cultural crossroad in the Adriatic Sea during the Dark Ages, between Byzantins, Lombards, Carolingians and local constructive traditions.
In the Adriatic regions, particularly in the city of Zadar in Croatia, different cultural influences overlapped between the 6th and 11th century AD. These regions are located between the Byzantine world, which was destined to carry on the ancient constructive traditions, and the continental European world, in which a collapse of the entire cycle of production of the construction industry occurred at the time. On the one hand, these regions are key to understanding the routes crossed by technological innovations, which lead, in the West, first to the Carolingian building sites and then to the Romanesque revolution. On the other hand, Zadar is an important site that could shed light on a coastal economic zone of the Mediterranean world, which in the Early Middle Ages seemed to be vital. In addition, the most important matches between the two empires occur here, and this central role of Zadar and of Dalmatia is well reflected in the architecture, which displays different cultural inputs.
The specific case analysed here, the architectural complex of St. Andrew and St. Peter the Elder's in Zadar, is an example of functional transformation of a sector of the ancient city linked with the new economic, political, and social dynamics taken over from the Early Middle Age. By rereading past investigations and employing a stratigraphic analysis of the standing buildings, the evolution of the complex from the Late Antiquity until the Modern Age was determined, along with document elements of continuity with the ancient city. A new interpretation of its stratigraphic sequence is possible, and by comparing the constructive techniques with other architectural contexts, the site can become part of a wider debate about early medieval architecture, different technological backgrounds, and geographies of power.
In this paper, the 1960s’ interpretation of constructive phases and chronologies of the complex are revised. Then, the constructive techniques are examined to collect elements to date the interventions and to better understand the workforces engaged in the different building sites. The plan and the vaults of St. Peter the Elder's are specifically discussed because they represent original and significant products for the history of constructive techniques.
This context is not only an expression of constructive techniques overlapping in time, but it also represents a window to the changes occurring in Zadar during the Early Middle Age and could be a key to reading a parallel historical process that involves the entire Dalmatia and the Adriatic regions.
THE STRATIGRAPHIC SEQUENCE
The churches of St. Andrew and St. Peter the Elder's are located at the crossroads between a cardo and decumano minor of the ancient city, within walking distance of the episcopal complex. Together, they make an architectural complex consisting of two buildings: the church of St. Peter the Elder's to the E and the church of St. Andrew to the W (Fig. 1). These buildings are featured by a long stratigraphic sequence, which includes important early medieval interventions. In addition, the case study is an example of functional conversion of previous buildings arisen inside the Roman settlement and later transformed into a place for Christian worship. Other interesting aspects include the type of plan and the system of vaults in the eastern building, which are peculiar of the regional architecture of the time.
Fig. 1 - Zadar, church of St. Andrew and St. Peter the Elder's. Localization of the complex at the crossroads with a cardo and decumano minor of the ancient city.
The first studies, dating to the end of the 19th century, were undertaken by Federico Bianchi (1877), Lorenzo Benevenia (1890), T. G. Jackson (1887), and Giovanni Smirich (1894: 21).
Excavations were carried out during the restoration works realized by the Jugoslovenski institut za zaštitu spomenika kulture, between 1961 and 1963. These essays brought to light some fragments of an early medieval liturgical furnishing, apparently belonging to the church of St. Peter. An ossuary tomb was discovered outside , and two layers of paintings were documented in the vaults and apsidal basin of St. Peter and in the apse of St. Andrew.
These discoveries were published only in 1970 by Ivan Petricioli and Svetislav Vučenović, directors of the excavation and restoration works. In their paper, they propose a stratigraphic analysis of the standing buildings, accompanied by sections, planimetries, and prospects that simultaneously show the different constructive phases. Despite the remarkable methodological approach, innovative for those years, there are some weak points in the sequence. However, no one discusses these sequences any longer, preferring instead to concentrate the debate on the chronology of the interventions, the liturgical furnishing, or the function of the eastern building (Goss 1987; Jurković 1997: 77-80; ibidem 2002: 197-205; Jakšić 2009: 61-93, 82-85; Marasović 2009) .
A review of the 1970 interpretation is presented here. This review highlights the critical points and proposes a different solution to the stratigraphic sequence, as well as some new chronologies.
The stratigraphic sequence in the Petricioli-Vučenovićs' interpretation of 1970
According to Petricioli-Vučenovićs' interpretation (Petricioli et al. 1970), the western church, which was partially rebuilt in the 17th century and dedicated to St. Andrew, is more ancient then the eastern one, and its foundation dates to the 5th or 6th century.
The eastern building was added just after the western one and originally was a sacristy; only later, during the 8th or 9th century was this last converted into a church dedicated to St. Peter, by creating two apses in the eastern side and building a system of vaults that divides the room into two aisles. In the end, the two buildings were decorated with frescoes, while the two entrances opening in the apse of St. Andrew were added later.
The dedication to St. Peter, which has appeared in written sources since 818 AD (Bianchi 1887: 380; Benevenia 1890: 99), originally referred to both churches. In addition, at the beginning of the 12th century, the church became St. Peter 'the Elder's' because a new church was built in Zadar with the same dedication. After the partially rebuilding of the western building, and its consecration to St. Andrew in 1684 (Petriocioli et al. 1970: 182; Vežić 2015: 152-153), two different dedications were made, and consequently, only the eastern church kept the original dedication to St. Peter.
1 - The western building (today St. Andrew) is more ancient than the eastern one (today St. Peter the Elder's)
Petricioli and Vučenović argue that the western building is more ancient than the eastern one because Smirich, during the excavations in the apse of St. Andrew, saw that the foundations were unexpectedly deep (Smirich 1894: 22-23), without any other indication; however, in the Smirich's interpretation the earlier building is the eastern one.
The two scholars then observed traces of a single pitch roof in the exterior of this apse (Fig. 2), which they attributed to the eastern building built later and leaning against the St. Andrew church. However, the roof may have been simply rebuilt when the entire sector was transformed with the addition of the new western church. Moreover, the traces consist of fragments of schist englobed in the apse, belonging to a single or two pitch roof, which therefore would be more ancient than or contemporary to the church of St. Andrew.
Fig. 2 - Zadar, apse of St. Andrew. Fragment of schist englobed in the external side, originally belonging to a roof.
Another element that contrasts with their interpretation is that the apse has no windows, except for a small square opening situated in a marginalized position in the upper part of the wall, exactly over the embedded traces of the roof. Thus, the apse was designed when the eastern building already existed, or during its construction, and the window was inserted in the only place the apse could be directly illuminated from the outside.
Moreover, along the south wall of the church of St. Peter, in the narrow space behind this semi-circular apse, there is a walled suspended entrance to which belonged two stones shelves still in situ. These stones could originally have had to support a wooden balcony or a staircase that surely were previous to the apse (Fig. 3).
Fig. 3 - Zadar, St. Peter the Elder's. Aerial entrance closed in the south perimeter wall, shown by inside (first period).
Finally, the planimetry of the complex shows a clearly visible anomaly created by the south perimeter wall of the church of St. Peter, which partially incorporates for a few meters the western building and maintains the same thickness until the end, where is abruptly interrupted. Petricioli and Vučenović do not deny that this south wall could be more ancient than the church of St. Peter and could be dated even to the Late Antiquity (Petricioli et al. 1970: 186; Vežić 2015: 157).
2 - The western church (today St. Andrew) dated to the 5th or 6th century
The dating to the 5th or 6th century is not based on strong arguments, but rather on the constructive techniques and on Smirich's affirmation about a possible and generic antiquity of the St. Andrew church because of the depth of its foundations.
However, an early medieval fragment of a liturgical furnishing decorated with weave pattern, walled in the right jamb of the apse and partially covered by two layers of plaster, one with frescoes, lowers the chronology of this building  (Fig. 4). Also, the stone shelf on which rests the triumphal arch, that is the same as those used to rest the vaults in the back building, indicates the same thing.
Fig. 4 - Zadar, St. Andrew. Fragment of liturgical furnishing dated to the Early Middle Ages, walled in the jamb of the triumphal arch (on the lower-right and in detail - a) and shelf identical to those of the vaults in St. Peter the Elder's (on the right - b).
Furthermore, the imprecision of the apse basin does not have any confront in the Late Antiquity, but it seems to be chronologically later.
3 - The eastern building was converted from sacristy to church by adding two apses and a system of vaults
According to the 1970 interpretation, the two rectangular inscribed apses and the cross vaults were realized at the same time, during a renovation of the eastern building, which was converted into a church possibly between the 8th and 9th centuries.
Instead, some elements suggest the existence of two interventions distant in time. These interventions consist first of the construction of the two apses with their basins and, later, also of the vaults that divide the room in two aisles. The elements are:
- The apsidal basins are lower than and out of proportion to the vaults, and the constructive technique is more imprecise because it used fewer provisional wooden supports during the construction;
- The constructive technique of the wall that divides the apses is characterized by imprecise masonry, which uses smaller stones than those of the pillars leaning against the perimeter walls; therefore, the edges are irregular and tapered;
- The vaults rest on the dividing wall of the apses apparently by breaking it, so they seem to have been added later;
- The vault supports are coeval with a floor, which is 20 cm higher than the ancient one maintained inside the church of St. Peter the Elder's ; in addition, one semi-pillar was built leaning against a fragment of the more ancient enclosure of the presbytery, which is preserved in situ precisely for this reason (Fig. 5);
Fig. 5 - Zadar, St. Peter the Elder's. Semi-pillar of the system of vaults of the fourth period, built upon the more ancient presbytery enclosure of the second period.
- The fragments of schist incorporated in the apse of St. Andrew testify to an older phase for the eastern building, previous to the construction of the vaults but contemporary with the construction of the two apses or with the building site of the new western church.
4 - The entrances opened on the apse of St. Andrew were inserted later
According to Patricioli-Vučenović, originally the two adjacent buildings were not connected, and the two entrances of the apse were built in the Baroque Age by breaking the wall and removing pieces of the fresco that consequently were absent in those points.
Currently, only one of the entrances is preserved, the south one, but the north one is still visible in some historical photographs (Serra 1930: 535) and reproduced in drawings from the 1970s. One does not observe traces of voluntary removal of the frescoes, which are preserved now only in the apsidal basin. Furthermore, interfaces indicating the break of the wall for the addition of the south entrance are absent. One column of the system of vaults, moreover, leans against a jamb of this entrance (Fig. 6).
Fig. 6 - Zadar, apse of St. Andrew. Column leaning against a jamb of the entrance that connect the two churches, and walled holy water font.
In addition, Smirich, who made some excavation essays on the apses at the end of the 19th century, discovered the remains of an ancient passage deep under the south entrance (Smirich 1894: 22-23). This discovery suggests that the entrance was closed in the past, possibly substituted by other lateral entrances, and then re-opened after the apse had been painted. Also, a holy water font walled in the exterior of the apse, on the side of the entrance and just beyond the column (Fig. 6), could be explained by the existence of a passage for the priests directly from the apse; maybe a second entrance on the north perimeter wall, now partially rebuilt, was destined for the laity instead .
The existence of this direct connection between the two churches is another indication that the church of St. Peter the Elder's is the most ancient of the two.
5 - Before the 17th century the architectural complex was entirely dedicated to St. Peter
According to the theory that originally the complex was entirely dedicated to St. Peter, different dedications for the two buildings were introduced only after the reconstruction and consecration of the western church, entitled to St. Andrew in 1684. The conversion of the dedication from St. Peter to St. Peter the Elder's, in the 12th century, was instead a consequence of building a new church in Zadar with the same dedication .
This hypothesis is derived from the idea that the western church is the most ancient and would explain why the dedication to St. Peter is maintained only in the eastern building.
Another more plausible possibility is that this dedication originally belonged exclusively to the eastern church, which became St. Peter the Elder's when the new western church was built. Therefore, this western church would be the St. Peter the New, until its reconstruction and its new dedication in the 16th .
A new interpretation of the stratigraphic sequence of the complex
After a thorough revision of the drawings published in 1970, and after a stratigraphic analysis of the standing buildings realized on the field, a new architectural sequence and new chronologies have been proposed. This new interpretation has shed light on the development of this sector of the city in one of the most dark periods of its history.
The eastern and southern perimeter walls of the church of St. Peter the Elder's represent the most ancient remains of the complex and are characterized by a series of openings, later closed, referable to a ground level, which is 40 cm lower than the modern floor.
On the external eastern prospect, one can observe an arched window walled on the ground level and three arched windows in the first level. These last windows were partially rebuilt in 1957, after a sudden collapse of the upper part of the wall.
In the south perimeter wall (Fig. 8.2), one can observe the infill of an entrance on the ground floor. The threshold was found during the excavations of the 1960s, while in the upper level, there is a window and a suspended entrance. This entrance was equipped with stone shelves to support a wooden balcony or a staircase, and it was built by breaking the wall 2.90 m above the ancient ground floor (therefore 2.50 m above the paved floor exposed at present).
Moreover, removal traces in the most ancient walls, documented in the 1970 drawings and still visible in the exterior southeast corner, allow one to imagine a more articulated planimetry, maybe constituted by one or more adjacent buildings projected toward an open area along the cardo, from which it was possible to directly access both on the first floor of the buildings and on the ground floor (Fig. 7.1 and 9.1).
Fig. 7 - Zadar, churches of St. Andrew and St. Peter the Elder's. Hypothetical evolution of the complex in plant.
Fig. 8 - Zadar, church of St. Peter the Elder's. Internal prospect of the perimeter walls with constructive phases (drawings overlapped by Petricioli and Vučenović 1970).
Fig. 9 - Zadar, churches of St. Andrew and St. Peter the Elder's. Reconstruction of the hypothetical development of the complex.
The low elevations, compared to the modern paved road, as well as the presence of more phases visible in these walls, suggest a very high chronology. The archaeological excavations realized between 1961 and 1963 by Petricioli and Vučenović brought to light the Roman structures to more than 1 m from the floor of the church, at a level close to those of the first period. Therefore, it is possible that the most ancient phases of the church of St. Peter the Elder's belong to buildings rise inside the insula of the Roman city, in the Antiquity or Late Antiquity.
The fragment of funerary stele found englobed in the external side of the south perimeter wall (Petricioli et al.: 195) , indicating that the use of spolia was already widespread, suggests the structures were 4th to 5th century. This dating confirms the directors of the excavation theory. Many years later, Vežić also embraced this theory (Vežić 2015: 158-159).
In the open space overlooking the cardo, a room with a slightly irregular planimetry was created by building a perimeter wall that closes the space toward the north and runs parallel to the street  (Fig. 7.2). At the same time, doors and windows on the most ancient walls were definitely closed, and a new paved floor was realized 40 cm above the previous levels.
Furthermore, the presbytery was equipped with a stone enclosure of which a fragment is still preserved in situ, containing the niches to insert small vertical supports; other pieces discovered during the excavations, consisting of fragments of the architrave and tympanum, have been attributed to this enclosure.
Two rectangular inscribed apses were obtained in the eastern sector by adding a central wall with a niche on the frontal side and by reinforcing the lateral walls (Fig. 8.3). The apsidal basins, characterized by an irregular shape, were linked with the partially rebuilt perimeter wall by means of small squinches that allow the passage from a square to a half-dome (Fig. 10).
Fig. 10 - Zadar, St. Peter the Elder's. Squinch on the corner of the north apsidal basin.
At the same time, the three windows of the upper level of the eastern wall were closed or defunctionalized, while the presbytery might have been raised by a step and by a second step in the apses.
One can also hypothesize that the room was possibly shorter and lower than the previous building (Fig. 9.2).
These interventions turned an open space, delimited by a series of pre-existing buildings, into a church. Most scholars have argued that it was the most ancient church preserved in elevation of the entire Dalmatia, dated to the 7th or 8th century (Jackson 1887: 261-263; Canali 2010: 362; Serra 1930: 535). The fragments of a liturgical furnishing, such as a vertical support conserved in the Archaeological Museum of Zadar attributed just to this church, have been dated to the 9th century by Petricioli and Vučenović (Petricioli et al.: 194-195) and recently by Vežić (2015: 29-30). This hypothetical dating has led other scholars to propose the same chronology for the church of St. Peter the Elder's (Jakšić 2009; Jurković 2001: 165), while in other cases, the building has been generally interpreted as 'pre-Romanesque', without offering a more precise dating. According to Vladimir Goss (1987), the building would be an architecture of 11th century, instead. In other papers, Jurković (1997: 203-204) partially embraced this opinion and hypothesized that it is an external crypt obtained inside more ancient buildings during the 11th century. This external crypt theory has also been accepted by Vežić (2015: 161-162).
After the publication of Petricioli and Vučenović, which changed the interpretation accepted until then, the idea that the western building dated to the 5th or 6th century and was more ancient than the eastern one was not discussed but was uncritically accepted. Moreover, also the idea that the eastern church was the result of two constructive phases, consisting of the construction of the perimeter walls and the enclosure of the presbytery and then of the construction of apses and vaults, was unanimously accepted.
However, the construction of apses and system of vaults occurring in two distinct moments, rather than inside the same building site, would have created confusion between the scholars, producing incoherent chronologies and the absence of comparisons.
The construction of a first place of worship, consisting of a room with two inscribed rectangular apses and of an enclosure of the presbytery, occurred in the Early Middle Ages. While the fragments of the liturgical furnishing have been dated to the 9th century, the typology of planimetry is attested from the century before.
Generally, early medieval churches (dated between the 8th and 10th centuries) with two apses are documented in Veneto, particularly in the area of Vicenza (Colecchia 2009). Another example in the Upper Adriatic Sea is represented by the church of St. Platone in the Cres island (Čaušević-Bully 2013), while other more distant comparisons are in Lombardia, Piemonte (Garofano 2002: 159-162; Piva 2001), Switzerland (Sennhauser 2003: 117-118; 185-189; ibidem: 929), and the Byzantine Empire.
The examples are numerous, but until the 10th century, only the second church of St. Peter of Rosà (10th or 11th century), near Vicenza, also had a double aisle (Colecchia 2009: 303-307). In this case, however, apses and aisles had different widths .
The total absence of comparisons for churches with two apses and two aisles during the 8th and 9th centuries is an additional confirmation of the original absence of the vaults in the church of St. Peter the Elder's in Zadar.
More direct comparisons of churches with two rectangular inscribed apses are located in Istria: St. Mary little of Bale, dated between the end of the 8th and 9th centuries , and the second phase of St. Cecilia of Guran, dated generically post 7th and 8th centuries (Terrier et al.: 2014; 2013; 2012; 2011; 2010).
Therefore, this building site could be dated between the second half of the 8th century and the beginning of the 9th century and its liturgical furnishing would be more generally of the 9th century. From a broader point of view, this building could be part of the wide phenomenon of inscribed apses in the Upper Adriatic Sea from the 8th century, which is discussed later.
A new wider church was built immediately in the west, with a semi-circular free apse and a rectangular room of about 11x5 m (Fig. 7.3 and 9.3).
Partially rebuilt during the 17th century, and dedicated to St. Andrew, this church could coincide with the supposed St. Peter the New. Only the apse and the south perimeter wall, 5 meters high, remain of the original building.
In the same building site, the entire western space of the ancient church was transformed, and a building with a double pitched roof that enveloped the semi-circular apse was built to connect the two churches. The only window open in this apse was located in the lateral upper part, which was the only point from which the church could be directly illuminated from outside. An entrance coinciding with the present one would guarantee a direct connection between the two buildings. Some steps found during the 1960s excavations were situated between the semi-circular apse and the south perimeter wall of the ancient building (Petricioli et al.: 1970). These steps, moreover, could be coeval and would also demonstrate the presence of a direct connection outside.
These interventions would have determined a functional change of the more ancient church and the indication 'St. Peter the Elder's' could spread from that moment. The presence of a holy water font walled in the external wall of the apse (Fig. 6) to the north of the entrance, and compatible with the elevations of the second period, indicates that the first church’s function as place of worship remained; however, it could have been converted into a place to keep the relics, according to a hypothesis by Jurković (2002: 203-205).
Elements necessary for absolute dating do not exist, but some clues suggest a chronology of the end of 10th or 11th century:
- a carved fragment of the early medieval liturgical furnishing, dated to the 9th century, re-used in the wall of the right jamb of the apse, which represents a generic terminus post quem;
- the shelves of stone of the apse are the same as those used to realize the later system of vaults;
- from the 12th century in the written sources the indication «veteris» appears (Vežić 2015: 152), but it is absent in a testament from 918 A.D., which named only one church dedicated to St. Peter in Zadar;
- if the functional interpretation of the eastern building is exact, the external crypts spread only during the 11th century (Jurković 2002: 203);
- the close correlation between these interventions and those of the following fourth period, which different clues suggest date to the same century.
The following building sites carries on the same program of spatial redefining, which consists of the construction of a new church in the west as well as of the transformation of the back building to an external crypt.
In the fourth period, the ancient church was raised and extended by breaking down the connection to the forepart and entirely incorporating the apse of the St. Peter the New.
The most determining intervention consisted of a system of small cross vaults dividing the eastern room into three aisles, each with four square bays (including those behind the semi-circular apse) (Fig. 7.4 and 9.4).
In addition, the room was totally repaved, reaching the same elevation of the presbytery sector, 20 cm above the previous floor. Only the steps inside the apses were maintained.
After closing the western entrance connected to the outside with a transversal wall, a new entrance was opened along the south perimeter wall, together with a small square window (Fig. 8.1).
The window of the semi-circular apse, after losing its original function, was closed from inside, maybe due to the lowering of the apsidal basin. This intervention is deducible from some visible anomalies in the triumphal arch and in the section drawing by Petricioli and Vučenović, which illustrates the window was built just at the level of the basin’s curve (Petricioli et al. 1970).
These interventions allow to redefine the external crypt, according to the canons of the vaulted chambers that spread during the 11th century. Of these vaulted chambers, the crypt of the cathedral of Zadar is the closest example.
Furthermore, the constructive techniques of the system of vaults, discussed in the next section, suggest this dating.
The last dating clue is the reuse of a carved fragment maybe belonging to the presbytery enclosure of the 9th century, which is walled at the base of one of the sub-arches of the vaults, in the space behind the semi-circular apse, near the south corner.
THE CONSTRUCTIVE TECHNIQUES
Planimetries with inscribed apses: circulation and translation of models
After reviewing the existing literature, maps have been produced on the spread of the different typologies of churches with inscribed apses in the Upper Adriatic Sea and Dalmatia. Then, comparisons have been sought outside the considered area.
Although many chronologies are still uncertain, and the consulted literature cannot be considered complete, a preliminary and coherent picture is possible.
The first distinction has been made between semi-circular inscribed apses, which are the most widespread, and rectangular inscribed apses. Then, another distinction has been made based on the number of apses.
The first example of a church with three aisles, and three semi-circular inscribed apses, is the St. Elena's chapel in Jerusalem, dated to the 4th century, from which the typology spread in Syria in the 6th and 7th centuries (Bianchi 2007: 70-75). The same typology is documented then in Switzerland since the beginning of the 9th century, in Zalavar (Hungary) in the second half of the 9th century (Mordovin 2006) and, from the middle of the 10th century, also in the Netherlands, for instance, in the church of Saints Peter and Paolo of Oosterbeek (Oswald et al.: 245-246).
Between the first Palestinian and Syrian examples with three aisles, and those spread in the European continent with a single aisle, there are the church of St. Vigilio of Palse, in Friuli (Villa 2003: 553, 572), the church of St. Maurus in Poreč (Matejčić 2001) and the second phase of St. Sophia of Dvigrad, in Istria ( Brogiolo et al., 2003). All these churches have a single aisle and date to the 8th century (Fig. 11).
Fig. 11 - Spread of the churches with three semicircular inscribed apses, in the Upper and Middle Adriatic Sea.
Instead, outside the considered area, the typology with rectangular inscribed apses seems to not be documented, except for some Syrian basilicas of the 6th century. In addition to the churches with two apses (Fig. 12), like St. Mary Little in Bale and St. Cecilia in Guran, the typology with three apses in Istria is documented in the early Middle Ages (Fig. 13), and its prototype could be the Lombard temple of Santa Maria in Valle of Cividale, in Friuli (760 A.C.). In the 9th century, this last typology also spread to the Dalmatian hinterland, in the Croatian dukes' and princes' estates, in association with basilical planimetries. However, this typology is particularly known in the Istrian region and generally in the Upper Adriatic Sea, where the Lombards ruled for some time.
Fig. 12 - Spread of the churches with two rectangular inscribed apses in the Upper and Middle Adriatic Sea.
Fig. 13 - Spread of the churches with three rectangular inscribed apses in the Upper and Middle Adriatic Sea.
A suggestive hypothesis is that the spread of planimetries with inscribed apses in the Upper Adriatic Sea, from the 8th century, is connected to the Byzantine Iconoclasm, which caused the run of masons together with artists and artisans. Effectively, the typology is documented in the regions that do not adhere to the Iconoclasm, like the Lombard duchy of Friuli, the Byzantine Istria that depends on Ravenna or, from the 9th century, the Croatian principality ruled by the Carolingian dynasty. Planimetries with inscribed apses are not documented, instead, in the Byzantine Dalmatia that depends on the iconoclastic patriarch of Constantinople.
For such reasons, the church of St. Peter the Elder's represents a singular building in that coastal region, possibly realized during the iconoclastic crisis and expression of a technological background comparisons of which have to be sought in the Upper Adriatic Sea.
The system of vaults
The ceiling of the church of St. Peter the Elder's consists of small cross vaults realized upon formwork and characterized by strong sub-arches. The supports consist of semi-pillars leaning against the perimeter walls and of one pillar and two columns free in the centre (Fig. 14, 15).
Fig. 14 - Zadra, St. Peter the Elder's. Apses of the second period with the impost of the vaults of fourth period.
Fig. 15 - Zadar, St. peter the Elder's. System of vaults of fourth period.
In Dalmatia, in the estates of the Croatian dukes and princes where the Carolingian influence is strong, the constructive tradition of the pillars prevailed throughout the 9th century and stayed alive in the 11th century. In addition, in the coastal Dalmatia, the monumental rotunda of St. Donatus in Zadar, with its columns built with spolia, is an exceptional building site, where local masons likely worked together with allochthonous workers.
From the 11th century, while the great basilicas spread again in all the Upper Adriatic Sea, and an important and standardized production of capitals, shafts, and column basis newly began, in the coastal Dalmatia one can observe the progressive spread of the columns. For the entire 11th century, however, these columns were essentially made with reused Roman or Late Antique building materials. The closest examples are the churches of St. Laurence and of St. Dominic in Zadar, as well as the crypt of the Cathedral. In the regional area, the St. Martin's church in Traù, or the basilica of Saint Euphemia are other examples.
In addition to the presence of the columns, the other special feature of the vaults of St. Peter the Elder's are the sub-arches, which are a structural element elaborated in the regions of the Byzantine Empire. These sub-arches made it possible to build self-bearing cross vaults and to continuously reuse the same formwork, thus saving on the cost of the wood.
In the West, the sub-arches of the vaults seem not to arrive before the 11th century. It is significant that the first systems of vaults of the hall crypts, dated to the end of the 10th and the beginning of the 11th centuries, do not have these constructive elements and consist instead of crossed barrel vaults of different heights or not perfectly closed in the centre. The system of vaults in the crypt of the Cathedral of Zadar belongs just to this last typology. However, in the 11th century, in Croatia, the sub-arches spread and can be observed in the St. Laurence of Zadar, or in the St. Martin of Traù. In Istria, these structural elements are in the only hall crypt of the region, which is the church of St. Pelagius in Novigrad, and in the episcopal complex of Poreč in front of the trichora, where they probably had to support a higher level.
However, there is a singular characteristic of the sub-arches of the St. Peter the Elder's: along the perimeter walls, they are not supported by stone shelves or semi-columns, as in all the other examples, but by semi-pillars. We still know little about the architecture developed in the Croatian principalities since the 9th century, and the remains sufficiently conserved in elevation are few. However, the long tradition of pillars in these regions of the Dalmatian hinterland suggest that the typology of the vault system of the St. Peter the Elder's derived from here.
ZADAR: A CROSSROADS IN THE ADRIATIC SEA
The application of the stratigraphic method in the study of the architecture, together with the analysis of the constructive techniques, has allowed one to follow the development of a small urban context in a diachronic way. New elements have been provided to investigate the transformation and reorganization of the city since the Late Antiquity; these elements are even more important because relating to a settlement where, because of the absence of extensive archaeological excavations, and because of too invasive restorations, it has not been possible to document the Early Medieval phases (Majocchi 2010).
The analysis of the complex of St. Andrew and St. Peter the Elder's demonstrates a settlement continuity and the maintenance of the urban scheme gave by the ancient cardi and decumani, together with a progressive, but controlled, growth of the ground level.
If the 'structural pattern' of the city does not change, as the maintenance of the ancient streets demonstrates, what changes is the 'significance' of the urban spaces. One can observe the functional conversion of some areas of the city, which in the case under examination consists of the transformation of a house into a place of Christian worship.
However, the critical revision of the stratigraphic analysis realized in the 1970s would postpone the radical functional transformation of this urban sector by almost two centuries. The fragment of a funerary stele, walled in the most ancient structures, suggests a date of the first period of the complex to the 4th or 5th century, or even later. Furthermore, the opening of an aerial entrance and other interventions in the pre-existing walls indicate a prolonged use of this building as house or storage.
A functional and structural transformation occurred only from the second half of the 8th to the beginning of the 9th century, when a church was obtained in the free space along the cardo minor.
The technological background of the workers engaged in this building site seem to have more contact with the regions of the Upper Adriatic Sea than the Byzantine area. Constructive techniques, planimetry and sculptural furnishing indeed are the same as the coeval architecture of Istria and northeast Italy. Moreover, the presence of a Lombard component in Dalmatia, also before the Carolingian one, had been recognized by scholars in the sculptures of the maestro degli amboni zaratini, working between the second half of the 8th and the first years of the 9th century in Zadar and Pridraga (Josipović 2016).
In the city of Zadar, another imposing building site of crucial importance soon began: the rotunda of the Holy Trinity commissioned by the bishop Donatus, possibly as a crowning of the Aachen Treaty of 812, which diplomatically regulated the influence sphere of Byzantines and Carolingians in the Adriatic Sea. The building site involved allochthonous workers, almost certainly of Byzantine provenance, and maybe local masons. The instruments and technical skills to lift high columns and install the large squared stones of the pillars, then finished on site, as well as the planning complexity behind the entire building, characterized by golden proportions and complicated geometries, both belong to a technological background only existing in the Byzantine Empire. However, if specialized workers worked on the most important structural elements, the perimeter walls instead, characterized by irregular arrangements made of simply broken reused limestones, allow one to also hypothesize the activity of local masons on the building site. The masonry technique, as well as the irregularity of some planimetric drawings, suggest that these local workers exported the characteristic model of churches with radial apses to all the Dalmatia, along the coast as well as in the Croatian principalities of the hinterland, on the wave of the widespread rotundas also occurring in the West, starting from the 9th century. It is significant that just in the city of Zadar is preserved one of the most ancient churches with radial apses: St. Mary in Stomorica's church built just outside Roman and Early Medieval walls (Zanetto 2017: 138-142; 221-223).
As these few examples demonstrate, the boundary between the Roman-Byzantine Dalmatia and the Slavic one is unclear, either before or after the Aachen Treaty. Furthermore, during the 7th and 8th centuries, there was a progressive process of integration and pacific coexistence between the two worlds (Goldestein 2005). It even seems that the city of Zadar, during the entire Early Middle Ages, was a crossroads of different constructive traditions that interacted with a local substratum.
The system of vaults of St. Peter the Elder's, dated to the 11th century (fourth period), that put together pillars and reused columns, sub-arches and standardized cross vaults, represents the integration of many constructive techniques and technological backgrounds once again.
If the architecture can provide a reliable key to understanding the historical and economical processes, it can be said that the city of Zadar represented a vital crossroads in the Adriatic Sea during the entire Early Middle Ages, despite the scarcity of monumental remains. However, the few material remains can enrich this picture further, but an archaeological approach, absolute datings, and analysis free from ideologies are needed.
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 An earring of the 11th century, a small coin (not deciphered) and some other small finds were discovered in the ossuary covered by slabs (Petricioli et al. 1970: 177-202).
 Most recently only Pavuša Vežić has reviewed the sequence, however not changing the interpretation of 1970 (Vežić 2015: 151-170).
 Bianchi indicates the year 908, then corrected by Benevenia.
 T. G. Jackson (J1887:261-263) and Alessandro Dudan (1923), quoted in Canali (2010), p. 362) are of the same opinion.
 Vučenović and Petricioli interpret it as an improbable later addition.
 This paved floor stood at -90 cm from that of the Baroque age and was brought to light in the 1886 by Smirich, who reproduced it in his drawings (Vežić 2015: 155); in some historical photographs one can still observe the higher level of the floor, although partially covered with rubble (for instance Serra 1930: 534). During the restoration of the 1960s this floor was removed, reaching the previous levels of the church (at about -20 cm from the last), and discovering the basis of the supports for the vaults and a piece of the enclosure of the presbytery with the niches for the vertical supports.
 The hypothesis of the existence of entrances in the north side was already expressed by Pavuša Vežić, who agrees however with Petricioli e Vučenović about the idea that the two building were not in communication (Vežić 2015: 165-166).
 About this church, Bianchi in the 1877 claims that was located in the main square of Zadar (in plateis magna), near the Loggia; he also writes that the same building in 1154 was promoted to 'collegiata' grade and then demolished in 1447 (Bianchi 1887: 383). The plateis magna would correspond to the Piazza del Popolo, a political centre of the city from the 1289 at least, located 140 m southern from the complex in exam.
 See the new interpretation proposed by Pavuša Vežić about the previous dedication to St. Marina of the eastern church (Vežić 2015: 166-7).
 Only the window on the left is original (Petricioli et al.: 183).
 Petricioli, Vučenović, 'Crve Sv. Andrija', p. 195. The funerary stele was coinciding with the third bay, but it has been removed; its exact location remains unknown.
 Because of the numerous interventions, the stratigraphic relations of this wall with the other structures are not visible and neither the masonry technique; the external wall facing has been completely rebuilt indeed, as well as many parts of the internal perimeter wall.
 The step of the presbytery sector possibly had the same height of the basis of the enclosure, while that of the apses hid the basis of the dividing central wall.
 Marasović, Dalmatia praeromanica, p. 327.
 Examples of churches with two apses are documented also in Asia Minor, Georgia, Armenia, Cyprus, Aegean Islands and Greece (Dimitrokallis 1976).
 Castelletto di Brenzone near Verone (ending of 8th-9th centuries) is characterized by two aisles of different width and by three free semicircular apses, all different between them (Garofano 2002: 159-161). Other examples, for instance from the Corsica, Sardegna or Lunigiana regions, where churches with two apses and two aisles are particularly numerous, dated to 11th-13th centuries (Mortignoni 2011; Coroneo 2008).
 This dating considers the most recent proposal of Garofano, who dates it to the Carolingian Age (Garofano 2002: 163-164).
 "Dimitto in S. Pietro uno savano de panno serico" (Benevenia 1890: 99; Bianchi 1887: 380).
 A Smirich's drawing of 1887 documents this paved floor and the steps of the two apses.
 The first examples are the parish church of Zillis dated to around the 800 A.C. (Sennhauser 2003: 203-204), the Carolingian churches of St. Agata and St. Marie of Disentis (Ibid.: 80-86) and the church of St. Luzi in the diocese of Coira of the first half of the 9th century (Ibid.: 72-73).
 Also the planimetry of the first cathedral of Cittanova-Eracliana, in the lagoon, was characterized by three semicircular and inscribed apses, but the chronology proposed by Dorigo (7th century) is uncertain (Dorigo 1995: 301-304)
 The only exception is the church of St. Benedict in Malles, Trentino, dated to the first half of the 8th century; however, in this case the apses are a kind of niches in the wall (Nothdurfter 2001: 127).
 For instance the basilicas of di Khirbet Teizin (585 d.C.) or the eastern basilica of Baqirha (546 d.C.) (Lassus1947: 63).
 In the 9th century the typology is documented also in the duomo of Muggia (Trieste) and in the church discovered under the duomo of Visinada.
 Like the basilica of St. Mary in Biskupija, near the city of Tenin, and in that of Koliane, in the territory of Split.
 Examples dated to the 9th century are the church of St. Martha of Biiači and the basilicas of Koljane and of St. Mary of Biskupija, near Tenin; for the centuries 10th-11th the church of St. Stephan of Gospin Otok (Salone), the St. Peter of Dubrovnik and the basilica of St. Mary in Stupovi, near Biskupija.
 Among the most significant building sites there are the Cathedral of Aquileia, the Cathedral of Torcello (Veneto e Friuli Venezia Giulia) and the parish church of Sveti Lovreč (Istria).
 For instance the crypts of the basilicas of Aquileia and San Marco in Venice, for which the stratigraphic analysis suggests a high chronology (Zanetto 2017: 11-44, 44-57)
 This also applies to the transversal arches; a significant example are the arches of the ambulatory of the St. John's church of Arbe.